1. Field of the Invention
The present invention pertains to a method and system for treating well drilling cuttings and similar slurries of oily solids wherein the slurry is subjected to a drying process and wherein a mixture of liquid having residual solid fines entrained therein is processed through a rotary vacuum type filter, particularly a precoat type filter.
2. Background
The generation of oil and gas well drill cuttings slurries and similar slurries of oily liquids and solids has presented longstanding problems with respect to suitable treatment and disposal methods which are environmentally acceptable.
Slurries of oily liquid and solids mixtures may be subjected to a drying process wherein the material is exposed to a relatively intense heat source and agitated to thoroughly evaporate as well as sometimes chemically alter the liquids present in the slurry. The dried solids may then be discharged directly back to the environment, particularly in the case of earth drill cuttings. However, the vapors produced in such drying processes must be treated further since they normally include entrained solids fines and such vapors are either not acceptable for direct discharge into the atmosphere or can be reused in a drilling process or the like. To this end, several attempts have been made to provide condensing and separating processes for the vapors produced by the slurry drying process. However, the fineness of the solids mixed or entrained with the vapors, in many cases, is such that these solids are not easily separated by a gravity type separator or by a direct impingement type separator since the characteristics of the solids fines tend to blind or clog the impingement type filter media.
One important application of drill cuttings treatment systems is in offshore drilling operations wherein, if the dried drill cuttings solids have been rid of oil or other contaminants, they may usually be discharged directly back into the sea. In like manner, dried drill cuttings solids from land based drilling operations may also be discharged directly onto the earth's surface if they have been suitably rid of oil or other contaminating substances.
Accordingly, there has been a continuing effort to develop an improved treatment method and system for oily solids wastes, such as drill cuttings slurries and other slurries of solids and oily liquid mixtures, wherein the solids are completely rid of hydrocarbon substances or other substances which are not suitable for discharge directly into the environment but which are capable of being separated from the solids. The type of process and system being sought has also included the constraint that the system must be relatively compact and not require further transport or treatment of the materials discharged from the system. It is to this end that the present invention has been developed.